pool: cache the pool data

the cache function had been commented out while debugging
re-enable it now

Signed-off-by: AceLan Kao <acelan@acelan.idv.tw>
ticker: bitcoinwisdom API is down

bitcoinwisdom API is down, so switch to btc-e to get the ticker data.

Signed-off-by: AceLan Kao <acelan@acelan.idv.tw>